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Sunday, 28 January 2018

The first monkey clones produced by method that made DollySunday, 28 January 2018

The first primate clones made by somatic cell nuclear transfer are two genetically identical long-tailed macaques born recently at the Chinese Academy of Sciences Institute of Neuroscience in Shanghai. Researchers named the newborns Zhong Zhong and Hua Hua - born eight and six weeks ago, respectively - after the Chinese adjective "Zhonghua," which means Chinese nation or people. The technical milestone, presented January 24 in the journal Cell, makes it a realistic possibility for labs to conduct research with customizable populations of genetically uniform monkeys.

"There are a lot of questions about primate biology that can be studied by having this additional model," says senior author Qiang Sun, Director of the Nonhuman Primate Research Facility at the Chinese Academy of Sciences Institute of Neuroscience.

"You can produce cloned monkeys with the same genetic background except the gene you manipulated. This will generate real models not just for genetically based brain diseases, but also cancer, immune, or metabolic disorders and allow us to test the efficacy of the drugs for these conditions before clinical use."

CAPTION: This is a photograph of Zhong Zhong, one of the first two monkeys created by somatic cell nuclear transfer. CREDIT: Qiang Sun and Mu-ming Poo/Chinese Academy of Sciences.

Zhong Zhong and Hua Hua are not the first primate clones - the title goes to Tetra, a rhesus monkey born in 1999 through a simpler method called embryo splitting (Chan et al., Science 287, 317-319). This approach is how twins arise naturally but can only generate up to four offspring at a time. Zhong Zhong and Hua Hua are the product of somatic cell nuclear transfer (SCNT), the technique used to create Dolly the sheep over 20 years ago, in which researchers remove the nucleus from an egg cell and replace it with another nucleus from differentiated body cells. This reconstructed egg then develops into a clone of whatever donated the replacement nucleus.

CAPTION: This is a photograph of Hua Hua, one of the first monkey clones made by somatic cell nuclear transfer. CREDIT: Qiang Sun and Mu-ming Poo/Chinese Academy of Sciences.

Differentiated monkey cell nuclei, compared to other mammals such as mice or cows, have proven resistant to SCNT. Sun and his colleagues overcame this challenge primarily by introducing epigenetic modulators after the nuclear transfer that switch on or off the genes that are inhibiting embryo development. The researchers found their success rate increased by transferring nuclei taken from fetal differentiated cells, such as fibroblasts, a cell type in the connective tissue. Zhong Zhong and Hua Hua are clones of the same macaque fetal fibroblasts. Adult donor cells were also used, but those clones only lived for a few hours after birth.

"We tried several different methods, but only one worked," says Sun.

"There was much failure before we found a way to successfully clone a monkey."

The first author Zhen Liu, a postdoctoral fellow, spent three years practicing and optimizing the SCNT procedure. He tested various methods to quickly and precisely remove the nuclear materials from the egg cell and promote the fusion of the nucleus-donor cell and enucleated egg. With the additional help of epigenetic modulators that re-activate the suppressed genes in the differentiated nucleus, he was able to achieve much higher rates of normal embryo development and pregnancy in the surrogate female monkeys.

"The SCNT procedure is rather delicate, so the faster you do it, the less damage to the egg you have, and Dr. Liu has a green thumb for doing this," says Muming Poo, a co-author on the study who directs the Institute of Neuroscience of CAS Center for Excellence in Brain Science and Intelligence Technology and helps to supervise the project.

"It takes a lot of practice. Not everybody can do the enucleation and cell fusion process quickly and precisely, and it is likely that the optimization of transfer procedure greatly helped us to achieve this success."

The researchers plan to continue improving the technique, which will also benefit from future work in other labs, and monitoring Zhong Zhong and Hua Hua for their physical and intellectual development. The babies are currently bottle fed and are growing normally compared to monkeys their age. The group is also expecting more macaque clones to be born over the coming months.

The lab is following strict international guidelines for animal research set by the US National Institutes of Health, but Sun and Poo encourage the scientific community to discuss what should or should not be acceptable practices when it comes to cloning of non-human primates.

"We are very aware that future research using non-human primates anywhere in the world depends on scientists following very strict ethical standards," Poo says.

This work was supported by grants from Chinese Academy of Sciences, the CAS Key Technology Talent Program, the Shanghai Municipal Government Bureau of Science and Technology, the National Postdoctoral Program for Innovative Talents and the China Postdoctoral Science Foundation.

Tuesday, 6 October 2015

Age-related macular degeneration (AMRD) could be treated by transplanting photoreceptors produced by the directed differentiation of stem cells, thanks to findings published today by Professor Gilbert Bernier of the University of Montreal and its affiliated Maisonneuve-Rosemont Hospital. ARMD is a common eye problem caused by the loss of cones. Bernier's team has developed a highly effective in vitro technique for producing light sensitive retina cells from human embryonic stem cells.

"Our method has the capacity to differentiate 80% of the stem cells into pure cones," Professor Gilbert explained.

"Within 45 days, the cones that we allowed to grow towards confluence spontaneously formed organised retinal tissue that was 150 microns thick. This has never been achieved before."

In order to verify the technique, Bernier injected clusters of retinal cells into the eyes of healthy mice. The transplanted photoreceptors migrated naturally within the retina of their host.

"To date, it has been difficult to obtain great quantities of human cones."

His discovery offers a way to overcome this problem, offering hope that treatments may be developed for currently non-curable degenerative diseases, like Stargardt disease and ARMD.

"Researchers have been trying to achieve this kind of trial for years," he said.

"Thanks to our simple and effective approach, any laboratory in the world will now be able to create masses of photoreceptors. Even if there's a long way to go before launching clinical trials, this means, in theory, that will be eventually be able to treat countless patients."

The findings are particularly significant in the light of improving life expectancies and the associated increase in cases of ARMD. ARMD is in fact the greatest cause of blindness amongst people over the age of 50 and affects millions of people worldwide. And as we age, it is more and more difficult to avoid - amongst people over 80, this accelerated aging of the retina affects nearly one in four. People with ARMD gradually lose their perception of colours and details to the point that they can no longer read, write, watch television or even recognize a face.

ARMD is due to the degeneration of the macula, which is the central part of the retina that enables the majority of eyesight. This degeneration is caused by the destruction of the cones and cells in the retinal pigment epithelium (RPE), a tissue that is responsible for the reparation of the visual cells in the retina and for the elimination of cells that are too worn out. However, there is only so much reparation that can be done as we are born with a fixed number of cones. They therefore cannot naturally be replaced. Moreover, as we age, the RPE's maintenance is less and less effective - waste accumulates, forming deposits.

"Differentiating RPE cells is quite easy. But in order to undertake a complete therapy, we need neuronal tissue that links all RPE cells to the cones. That is much more complex to develop," Bernier explains, noting nonetheless that he believes his research team is up to the challenge.

Bernier has been interested in the genes that code and enable the induction of the retina during embryonic development since completing his PhD in Molecular Biology in 1997.

"During my post-doc at the Max-Planck Institute in Germany, I developed the idea that there was a natural molecule that must exist and be capable of forcing embryonic stem cells into becoming cones," he said.

Indeed, bioinformatics analysis led him to predict the existence of a mysterious protein: COCO, a "recombinational" human molecule that is normally expressed within photoreceptors during their development.

In 2001, he launched his laboratory at Maisonneuve-Rosemont Hospital and immediately isolated the molecule. But it took several years of research to demystify the molecular pathways involved in the photoreceptors development mechanism. His latest research shows that in order to create cones, COCO can systematically block all the signalling pathways leading to the differentiation of the other retinal cells in the eye. It's by uncovering this molecular process that Bernier was able to produce photoreceptors. More specifically, he has produced S-cones, which are photoreceptor prototypes that are found in the most primitive organisms.

Beyond the clinical applications, Professor Bernier's findings could enable the modelling of human retinal degenerative diseases through the use of induced pluripotent stem cells, offering the possibility of directly testing potential avenues for therapy on the patient's own tissues.

Thursday, 3 September 2015

An international team of scientists led from Sweden’s Karolinska Institutethas for the first time mapped all the genes that are activated in the first few days of a fertilised human egg. The study, which is being published in the journal Nature Communications, provides an in-depth understanding of early embryonic development in human – and scientists now hope that the results will help finding for example new therapies against infertility.

At the start of an individual’s life there is a single fertilised egg cell. One day after fertilisation there are two cells, after two days four, after three days eight and so on, until there are billions of cells at birth. The order in which our genes are activated after fertilisation has remained one of the last uncharted territories of human development.

Juha Kere is a Professor of Molecular Genetics
at

Karolinska Institutet. Credit: Ulf
Sirborn.

There are approximately 23,000 human genes in total. In the current study, scientists found that only 32 of these genes are switched on two days after fertilization, and by day three there are 129 activated genes. Seven of the genes found and characterised had not been discovered previously.

“These genes are the ‘ignition key’ that is needed to turn on human embryonic development. It is like dropping a stone into water and then watching the waves spread across the surface”, says principal investigator Juha Kere, professor at theDepartment of Biosciences and Nutrition at Karolinska Institutet and also affiliated to the SciLifeLab facility in Stockholm.

The researchers had to develop a new way of analysing the results in order to find the new genes. Most genes code for proteins but there are a number of repeated DNA sequences that are often considered to be so-called ‘junk DNA’, but are in fact important in regulating gene expression.

Treatment of infertility

In the current study, the researchers show that the newly identified genes can interact with the ‘junk DNA’, and that this is essential to the start of development.

Outi Hovatta is a Professor of Obstetrics and

Gynaecology at Karolinska Institutet. Credit:

Ulf Sirborn.

“Our results provide novel insights into the regulation of early embryonic development in human. We identified novel factors that might be used in reprogramming cells into so-called pluripotent stem cells for possible treatment of a range of diseases, and potentially also in the treatment of infertility”, says Outi Hovatta, professor at Karolinska Institutet’s Department of Clinical Science, Intervention and Technology, and a senior author.

The study was a collaboration between three research groups from Sweden and Switzerland that each provided a unique set of skills and expertise. The work was supported by the Karolinska Institutet Distinguished Professor Award, the Swedish Research Council, the Strategic Research Program for Diabetes funding at Karolinska Institutet, Stockholm County, the Jane & Aatos Erkko Foundation, the Instrumentarium Science Foundation, and the Åke Wiberg and Magnus Bergvall foundations. The computations were performed on resources provided by SNIC through Uppsala Multidisciplinary Center for Advanced Computational Science (UPPMAX).